[118.03U] A Study of the Pulsar Emission Region at Multiple Frequencies

Observations taken simultaneously over three frequencies
(240, 325, & 610 MHz) with the GMRT in India, of the pulsar
PSR B3029+54 reveal a general trend for the core component
of high intensity pulses to arrive earlier than for less
intense pulses. Statistical analyses of the data also show a
trend that this phase shift of the core decreases at the
higher frequencies. Similar analysis of simultaneous data
taken over a larger frequency range (240, 610, 1410, & 4850
MHz, using the GMRT in combination with the Jodrell Bank and
Effelsberg telescopes) confirms this trend, with the shift
almost vanishing at the highest frequency. Analyses of PSR
B1642-03 (simultaneous at 240 & 610 MHz) and of PSR
B2111+46 (at 320MHz) also show similar intensity dependent
phase shifts. Thus, this may be a generic effect for the
core component emission of pulsars. Our analysis when
applied to the strong, conal pulsar PSR B1133+16 (at 240,
610, 1410, & 4850 MHz) show no apparent trend of phase
shift across frequency or intensity for the conal
components. We argue that these findings support the
hypothesis that, for core components, more intense pulses
originate at higher altitudes in the pulsar magnetosphere
than less intense pulses. The range of variation is found to
be 140 to 2100 kilometers.

This research was funded by an REU grant from the National
Science Foundation through Cornell University. Research took
place at Arecibo Observatory, operated by Cornell University
under contract to the National Science Foundation.

The author(s) of this abstract have provided an email address
for comments about the abstract:
boye0010@umn.edu